Season 1: Man Against Nature, the Losties arrive on the Island and it's not the paradise they thought, there's something weird here, but they still need to survive. Key Flashbacks: all the Losties.
Season 2: The Hatches and the mystery of the Others. Tailies subplot. Key Flashbacks: Ana Lucia and Eko
Season 3: The drama of the Others and their relationship with the Losties. Desmond subplot. Key Flashbacks: Desmond, Juliet and Ben (though I also loved Expose)
Season 4: There is a supernatural force on the island. Widmore (or the outside world looking in) subplot. Key Flashbacks: Richard Alpert and Tom.

I believe that the Jacob scene in this episode set us up for the investigation of supernatural forces on the island. I think this is the "We have a Locke Problem" quote that Jack uttered way back when.

So to me what we saw in this episode was the introduction, not to Dharma, but to this mysterious group of Hostiles. The issues in Season 4 won't be about Dharma, they will be about the Black Rock, the ruins, and mysticism.

That still leaves 32 episodes for zombies.

Don